1. Field of the Invention
The present invention relates to an infinitely variable mechanical power transmission system.
2. Description of the Prior Art
Conventional mechanical power transmission systems include adjustments which allow the mechanical advantage of a power transmission to be adjusted in large, incremental steps. For example, conventional transmissions employed in automotive vehicles typically include three, four or five step wise adjustments that allow power to be transmitted at corresponding different mechanical advantages. Adjustment of mechanical advantage of power transmission is desirable, since power sources, such as internal combustion engines, provide power outputs that vary nonlinearly with engine speeds. Therefore, the transmission of power which is suitable at one mechanical advantage for an engine operating at a low speed is not suitable for the transmission of power from the same engine operating at a higher speed.
In conventional power transmission systems, each incremental step or adjustment in the transmission of power from a rotary shaft involves separate gear systems which are alternatively engageable for transmitting power from a rotary input shaft at a predetermined mechanical advantage. The choices of mechanical advantage are extremely limited, and are ideal only for specific engine speeds within the total range of engine speeds. Thus, conventional mechanical power transmissions necessarily operate at optimum efficiency only during the very small intervals of time at which the engine is operating at the specific speed for which the selected transmission gear system is optimally suited. At all other times power is transmitted at a reduced efficiency.
Various different infinitely variable rotary power transmission systems have been devised to transmit power at infinitely variable selections. For example, U.S. Pat. No. 4,616,478 describes a rotatable hydrostatic transmission in which the mechanical advantage of power transmission is varied using a hydraulic fluid transmission system. However, hydraulic fluid transmission systems are susceptible to failure due to hydraulic fluid leaks. Furthermore, such systems often involve significant power losses due to high fluid friction since there is a considerable amount of hydraulic fluid flow through very narrow hydraulic fluid transfer lines and passageways.